The present invention relates to deadman control systems for self-propelled, walk-behind implements and more specifically relates to combined control lever and ignition interlock switch designs.
The present invention is concerned with safety interlock control systems designed for limiting the possibility that an operator of a self-propelled, walk-behind implement will come into contact with the tool of the implement when the tool drive is engaged while the engine is running. U.S. Pat. No. 4,062,135 issued to the applicant of the instant case on Dec. 13, 1977 is an example of such a control system. The implement disclosed in this patent is a snowblower including a collector-impeller as a driven tool. Separate control levers are provided on the guide handle structure for controlling the traction and collector-impeller drives and ignition interlock switches are operated by the levers such that the engine is "killed" in the event that the operator releases the traction drive control lever while the collector-impeller drive is engaged.
The patented design has the disadvantage of requiring the operator to place the collector-impeller drive control lever in an intermediate position between fully-released and engaged positions in order for the collector-impeller to remain engaged when the traction drive is disengaged and this requirement has proved to be awkward for operators to accomplish.